Reply to Benjamin. The best worms for compost bins are brandling worms, Eisenia fetida, rather than the lobworm or earthworm. These are available from the companies that sell wormeries and compost kit.
Try here:
http://www.wigglywigglers.co.uk/

Reply to Linmos. The most important thing about nest boxes is that they should be in a position in which the birds feel safe. These boxes are for birds that normally nest in natural hollows in old trees, cliffs and gullies. Although some nest boxes are marketed specifically to attach to windows for interior viewing, this goes against my intuition. I think the best place to put these boxes is in secluded secret places, hidden on a fence under clematis or ivy, high up in trees in dense foliage. North-facing is probably the least attractive, since this is the wet and cold side. Hope this helps.